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根据野外水准测量与室内实验分析,本文探讨了西藏纳木错和藏北高原古大湖晚更新世以来的湖泊演化和气候变迁。在纳木错沿岸拔湖48m以下,发育了6级湖岸阶地,拔湖48～139.2m发育有高位湖相沉积。研究表明,纳木错湖泊发育与藏北高原东南部古大湖演化可划分为3个阶段:①116～37kaB.P.间的古大湖期;②37～30kaB.P.间的外流湖期;③30kaB.P.以来的纳木错期。在古大湖阶段,包括纳木错、色林错和扎日南木错、当惹雍错等藏北高原东南部的一大批现代大、中、小型湖泊,都是互相连通的一个古大湖,其范围可能超过了现代的藏北内、外流(怒江)水系的分水岭。它或许还与藏北高原南部和西部的其他古湖相连,成为统一的藏北高原“古大湖”。通过对纳木错湖相沉积形成时代与深海氧同位素对比,易溶盐、pH值、地球化学、介形类和孢粉分析等的综合研究发现,湖相沉积记录了自晚更新世以来的湖泊演化和气候变迁信息。资料显示古大湖期湖面最高,气候温和清爽;外流湖期湖面急剧下降,气温和湿度较现今略高;纳木错期以来气候经历了全新世最宜期的暖湿后日益干旱化,气温波动,湖面持续下降。表明自晚更新世以来该区气候在逐渐变干的总趋势的基础上,经历了多次明显的冷暖与干湿波动。
According to the field leveling and laboratory analysis, this paper discusses the lake evolution and climate change since the Late Pleistocene of the Great Lakes in the Nam Co of Tibet and the Great Northern Tibet Plateau. In the Nam Co Lake 48m below the lake, the development of the lake shore terrace 6, pull the lake 48 ~ 139.2m development of high lacustrine deposits. The study shows that the development of the Nam Co Lake and the evolution of the Paleozoic Lake in the southeastern Tibet Plateau can be divided into three stages: (1) the Great Paleozoic during the period of 116 ~ 37 kaB.P; (2) the outflow lakes between 37 and 30 kaB.P; Namco since the wrong period. In the ancient Great Lakes stage, a large number of modern large, medium and small lakes, including the Nam Co, Sehrin and Zaram Nam Co, Yogyakarta, etc, southeast of the northern Tibet Plateau, are connected with each other through a large ancient lake. Its scope Probably surpassing the watershed of the modern interior and outflow (Nujiang) river systems in northern Tibet. It may also be connected to other ancient lakes in the southern and western parts of the northern Tibet Plateau to become the “ancient Great Lakes” of the unified northern Tibet Plateau. Through the comprehensive study of the sedimentary ages of the Nam Co Lake and the deep-sea oxygen isotopes, the study of the soluble salts, pH values, geochemistry, ostracods and sporopollen analysis, it is found that lacustrine sediments recorded the evolution of lakes since the late Pleistocene And climate change information. The data show that the lake has the highest level in the Great Great Lakes and the climate is mild and refreshing. The lake level drops sharply during the outflow lake period, and the temperature and humidity are slightly higher than those of the present day. Since the Namco fault period, the climate experienced the easterly, keep falling. This shows that on the basis of the general tendency that the climate in this area has gradually dried up since the late Pleistocene, it has undergone several obvious fluctuations in the warm, cold, dry and wet conditions.